The present article seeks to investigate the origin of teachers' training in high school from the history of education. The origin of this training goes back to a particular historical moment which the historiography has labelled "Conservative Republic". This way, we try to analyze a set of reforms that are produced within the conservative government framework and driven by change demands that Argentinian middle classes put forward. Within the educational field, those demands are focused on secondary education and their aim is to cause changes not only in level but in their teachers' training.